JP2015223463A - Lighting system, lighting method, and endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the dimension of speckle noises observed in each color (waveform) by reducing the speckle noises by a further simple method.SOLUTION: The lighting system includes: at least one laser light source for exiting laser beams; optical fibers which the laser beams exited from the laser source enter; and a diffusion member diffusing the laser beams exited from the optical fibers to generate a secondary light source. The laser beams enter an incidence end face of the optical fibers from an oblique direction with respect to a normal line of the incidence end face.

Description

  The present disclosure relates to an illumination device, an illumination method, and an endoscope.

  The optical system of the endoscope includes a light source, a condensing optical system, a light guide that is a bundle fiber in which optical fibers are bundled, and an illumination optical system. In general, lamp light sources such as xenon lamps and halogen lamps are often used as light sources for endoscopes, and the light from the lamp light sources is coupled to a light guide to insert an endoscope as a patient wearing part. By connecting the light guide to the tip part of the unit, light is irradiated from the tip part of the light guide to the observation part.

  However, especially lamp light sources such as xenon lamps have large power consumption and heat generation. Moreover, since the lamp light source has a very wide light distribution angle, the light efficiency is poor. Therefore, in recent years, a laser is used as a light source for an endoscope instead of a lamp light source.

  Advantages of using a laser as a light source are (1) a high light-electric conversion efficiency of the light source and a high light coupling efficiency to the light guide, and so on. Because of its high directivity, the optical coupling efficiency to the small-diameter light guide is high, and it becomes possible to realize a small-diameter endoscope insertion part. (3) Since the wavelength width is narrow, In combination with the light absorption characteristics of the tissue, it is easy to emphasize and observe a specific tissue.

  However, when an irradiation field is observed by illuminating an object with light emitted from an illumination device using a laser as a light source, a bright and dark spot pattern may appear due to the high coherence of the laser light. . This speckled pattern is called speckle noise and can hinder irradiation field observation.

  In order to obtain an observation image with little occurrence of speckle noise, various techniques as exemplified in Patent Documents 1 to 5 below have been proposed.

  For example, Patent Document 1 below discloses an endoscope system that uses a bundle fiber obtained by bundling a plurality of optical fibers having an optical path difference length equal to or greater than a coherence length as a noise reduction device.

  For example, Patent Document 2 below discloses an endoscope light source device that uses a plurality of modules that output intensity-modulated laser light through optical fibers, bundles the optical fibers, and further optically couples them into a single optical fiber. Has been.

  For example, Patent Document 3 below discloses an illuminating device including a high-frequency superimposing unit that superimposes a high-frequency signal on a drive current supplied to a semiconductor laser that is a light source to oscillate the semiconductor laser in a multimode.

  For example, Patent Document 4 below discloses an endoscope in which a vibrating means for vibrating an optical fiber is disposed in an endoscope insertion portion.

  For example, Patent Document 5 below discloses an endoscope system that performs image processing on an obtained captured image and outputs it as an observation image.

JP 2008-043493 A JP 2009-240560 A JP 2010-042153 A JP 2010-172651 A JP 2012-005785 A

  However, in the above Patent Document 1, a bundle fiber device whose strand length is equal to or longer than the coherence length, in the above Patent Document 2, a multi-fiber light source device and an intensity modulator, in the above Patent Document 3, a high frequency superposition circuit, and in the above Patent Document 4, a machine In addition to the configuration for realizing the functions of the image processing device and the lighting device in the above-mentioned Patent Document 5, in addition to the configuration for realizing the functions of the automatic vibration means, the entire device is enlarged and the speckle noise is reduced. Costs will be required separately.

  In addition, when obtaining a white light source, for example, laser light sources that emit red, green, and blue lasers are used. However, since the beam shape is different for each color (each wavelength) laser light source, the space caused by the beam shape is used. There is a problem that the speckle noise observed in each color (wavelength) is different.

  Therefore, in the present disclosure, in view of the above circumstances, an illumination device capable of reducing speckle noise by a simpler method and making the magnitude of speckle noise observed in each color (wavelength) equal. A lighting method and an endoscope are proposed.

  According to the present disclosure, at least one laser light source that emits laser light, an optical fiber on which the laser light emitted from the laser light source is incident, and the laser light emitted from the optical fiber are diffused. And a diffusing member that generates a secondary light source, wherein the laser light is incident on the incident end face of the optical fiber from an oblique direction with respect to a normal line of the incident end face.

  Further, according to the present disclosure, the laser light emitted from at least one laser light source is guided to an optical fiber, and the laser light emitted from the optical fiber is diffused by a diffusing element to be secondary. Generating a light source, wherein the laser beam is incident on the incident end face of the optical fiber from an oblique direction with respect to a normal line of the incident end face.

  According to the present disclosure, at least one laser light source that emits laser light, an optical fiber that receives the laser light emitted from the laser light source, and the laser light emitted from the optical fiber are diffused. And a diffusing element that generates a secondary light source. The endoscope includes an illuminating device that is incident on the incident end face of the optical fiber from an oblique direction with respect to a normal line of the incident end face. Is provided.

  As described above, according to the present disclosure, speckle noise can be reduced by a simpler method, and the magnitude of speckle noise observed in each color (wavelength) can be made equal.

  Note that the above effects are not necessarily limited, and any of the effects shown in the present specification or other things that can be grasped from the present specification together with the above effects or instead of the above effects. The effect of may be produced.

It is explanatory drawing which showed typically the structure of the illuminating device which concerns on 1st Embodiment of this indication. It is explanatory drawing which showed typically the incident end of the light guide. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing for demonstrating the positional relationship of the pupil position of a collector lens, and a laser beam. It is explanatory drawing for demonstrating the positional relationship of the pupil position of a collector lens, and a laser beam. It is explanatory drawing for demonstrating the positional relationship of the pupil position of a collector lens, and a laser beam. It is explanatory drawing for demonstrating the positional relationship of the pupil position of a collector lens, and a laser beam. It is the graph which showed the relationship between the shift amount on the optical axis of a dichroic mirror, and a speckle. It is explanatory drawing for demonstrating the positional relationship of the pupil position of a collector lens, and a laser beam. It is explanatory drawing for demonstrating the positional relationship of the pupil position of a collector lens, and a laser beam. It is explanatory drawing which showed typically the structure of the endoscope provided with the illuminating device which concerns on the embodiment. It is explanatory drawing which showed the lens data of the condenser optical system which concerns on the same embodiment. It is explanatory drawing which showed the lens structural example of the condenser optical system which concerns on the same embodiment. It is explanatory drawing which showed the lens structural example of the condenser optical system which concerns on the same embodiment. It is explanatory drawing which showed the lens structural example of the condenser optical system which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on 2nd Embodiment of this indication. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing for demonstrating the positional relationship of the pupil position of a collector lens, and a laser beam. It is explanatory drawing for demonstrating the positional relationship of the pupil position of a collector lens, and a laser beam. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on the same embodiment. It is explanatory drawing which showed typically the structure of the endoscope provided with the illuminating device which concerns on the embodiment. It is explanatory drawing which showed typically the apparatus structure for verifying the relationship between the shift amount on the optical axis of a dichroic mirror, and a speckle. It is the graph which showed the relationship between the shift amount on the optical axis of a dichroic mirror, and a speckle. It is explanatory drawing which showed typically the apparatus structure for verifying the relationship between the shift amount on the optical axis of a dichroic mirror, and a speckle. It is the graph which showed the relationship between the shift amount on the optical axis of a dichroic mirror, and a speckle. It is explanatory drawing which showed typically the structure of the illuminating device which concerns on 3rd Embodiment of this indication. It is explanatory drawing which showed typically the structure of the endoscope provided with the illuminating device which concerns on the embodiment.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
1. About speckle noise 1st Embodiment (example which reduces the speckle noise of the whole illuminating device)
2.1. Configuration of lighting device 2.2. Configuration of endoscope 2.3. 2. Specific example of condenser optical system Second Embodiment (Example in which speckle noise of each light source is reduced, and portions related to spatial coherence in speckle noise observed with each light source are made equal)
3.1. Configuration of lighting device 3.2. Configuration of endoscope 3.3. Verification example 4. Third embodiment (combination example of the first embodiment and the second embodiment)

(Speckle noise)
Prior to describing the illumination device, the illumination method, and the endoscope according to the embodiment of the present disclosure, speckle noise (hereinafter, also simply referred to as “speckle”) focused on in the present disclosure will be briefly described.

  It is known that speckle noise depends on (a) the wavelength width of the light source that illuminates the observation region, (b) the luminance distribution of the light source that illuminates the observation region, and (c) the surface roughness of the observation region. It has been. Of these three factors, (a) relates to the temporal coherence of the light source, and (b) relates to the spatial coherence of the light source. Therefore, the speckle treated as a problem here relates to the spatial coherence of the light source.

  It is known that the coherence of an object surface illuminated by a light source having a luminance distribution S (ξ) follows the Van Cittert Zernike theorem expressed by the following Equation 1.

Here, in Equation 1 above,
x: position on the object plane μ: degree of complex coherence (parameter indicating spatial coherence between position x and (x + Δx))
S (ξ): Luminance distribution of light source i: Imaginary unit λ: Wavelength.

  As is clear from the shape of Equation 1, the spatial coherence of the object plane is given by the Fourier transform of the luminance distribution S (ξ) of the light source. That is, the spatial frequency spectrum of the luminance distribution of the light source is the degree of coherence. Therefore, if the light source is a point light source, the luminance distribution S (ξ) can be regarded as a δ function, and all points on the object plane interfere with each other, resulting in high coherence. Such a light source (point light source) is called a coherent light source. On the other hand, in the case of a uniform light source having an infinite size, the luminance distribution S (ξ) = 1, and the Fourier transform becomes a δ function, and interference occurs only at the same position on the object plane. Low. Such an infinitely large light source is referred to as an incoherent light source. The light source actually used in the illumination device is a partially coherent light source located between the spatially coherent light source and the incoherent light source, so that the apparent light source size is large and the luminance distribution of the light source is uniform. The more coherent, the lower the coherence.

  In recent years, a laser used as a light source has a narrow wavelength width and a small size of a light-emitting portion compared to a lamp light source because of its light emission principle, and thus has high spatial and temporal coherence of light. As a result, when a laser is used as the light source, speckle noise tends to be observed greatly.

  Here, in order to obtain white light using laser light, a laser device that emits R (red light), G (green light), and B (blue light), which are the three primary colors of light, can be used. It is conceivable that light is emitted by a laser device and blue-excited phosphor. However, since the near-field pattern (NFP) and the far-field pattern (FFP) are different for each color laser device, color unevenness occurs and spatial feasibility due to the beam shape is caused. As a result of the difference in coherence, the magnitude of speckle noise observed in each color is different.

  One of the invariants held in the entire optical system is a Lagrange invariant represented by the following formula 2.

L ₁ = φ ₁ × NA ₁ (Formula 2)
L ₁ : Invariant of Lagrange φ ₁ : Size of light source NA ₁ : Numerical aperture of light source (= n × sin Θ ₁ )
n: Refractive index Θ ₁ : Divergence angle of light source

  Here, an optical system using a laser has a small invariant of the Lagrange, so it is difficult to achieve both a large light source size and a large divergence angle required when coupled to a light guide.

  Accordingly, when realizing an illumination light source for an endoscope using a laser, it is required to fully consider the above points.

  When a coherent light source such as a laser is used, if the beam diameter is reduced with emphasis only on improving the optical coupling efficiency to the light guide relative to the incident end of the light guide, coherent interference is evident from the above explanation. And speckle noise is more likely to occur. As a speckle reduction measure, conventionally, as shown in Patent Documents 1 to 5, speckle noise can be reduced by adding a further mechanism to the lighting device.

  However, as a result of intensive studies on the above contents, the present inventors have conceived that speckle noise can be reduced more easily by paying attention to the beam diameter and luminance distribution of the laser light, and will be described below. The lighting device and the lighting method according to each embodiment of the disclosure have been completed. Hereinafter, an illumination device and an illumination method according to each embodiment of the present disclosure and an endoscope using the illumination device will be described in detail.

(First embodiment)
In the following, first, an illuminating device and an illuminating method capable of reducing the coherence of the entire illuminating device to make it difficult to generate speckle noise, and an endoscope having the illuminating device will be described in detail. .

<About the configuration of the lighting device>
First, the configuration of the illumination device according to the first embodiment of the present disclosure will be described with reference to FIGS. 1A to 9B. FIG. 1A is an explanatory diagram schematically illustrating the configuration of the illumination device according to the present embodiment, and FIG. 1B is an explanatory diagram schematically illustrating an incident end of the light guide. 2 to 3 are explanatory views schematically showing the configuration of the illumination device according to the present embodiment. 4 to 7 and 9A to 9B are explanatory diagrams for explaining the positional relationship between the pupil position of the collector lens and the laser beam. FIG. 8 is a graph showing the relationship between the shift amount on the optical axis of the dichroic mirror and the speckle.

  As schematically shown in FIG. 1A, the illumination device 1 according to the present embodiment includes a laser light source 100, a coupling optical system 110, an optical fiber 120, a collimating optical system 130, a diffusion member 140, and condenser optics. A system 150.

  At least one laser light source 100 is provided in the illumination apparatus 1 and emits laser light having a predetermined wavelength. In the illuminating device 1 according to the present embodiment, as the laser light source 100, various semiconductor lasers and solid-state lasers can be used, and a combination of these lasers and a wavelength conversion mechanism can also be used. Is possible. The wavelength of the laser light emitted from the laser light source 100 may be appropriately selected according to what kind of object or phenomenon is observed in the illumination target. Examples of such a wavelength include a visible light band having a wavelength of about 400 to 700 nm and a near infrared band used for ICG (Indocyanine green) fluorescence imaging. When such laser light is used as excitation light for fluorescence excitation, the observed fluorescence may include autofluorescence at the excitation light irradiation site, drug fluorescence due to various fluorescent reagents introduced into the irradiation site, and the like. .

  The coupling optical system 110 is an optical system for optically coupling the laser light emitted from the laser light source 100 to an optical fiber 120 provided in the subsequent stage. The configuration of the coupling optical system 110 is not particularly limited, and various known optical elements may be appropriately combined so that the laser beam is optically coupled to the optical fiber 120. The laser beam can be coupled to the optical fiber. At least one condensing lens (collector lens) for optically coupling to 120 is provided.

  Further, when the white illumination light is realized by combining a plurality of laser light sources 100, the coupling optical system 110 is further provided with at least one dichroic mirror or dichroic prism in addition to the collector lens. The plurality of laser beams emitted from the plurality of laser light sources 100 are combined by a dichroic mirror or a dichroic prism to generate white light. The combined light is collected by the collector lens and coupled to the optical fiber 120.

  When a plurality of laser light sources 100 are used in combination, it is preferable that the numerical apertures of the laser beams incident on the optical fiber 120 are uniform. However, since the FFP of each laser is different, it is actually difficult to align. Therefore, in such a case, the coupling optical system 110 is provided with a numerical aperture adjusting unit for aligning the incident numerical aperture between the laser beams emitted from the respective laser light sources 100. The numerical aperture adjusting unit will be described in detail later.

  The optical fiber 120 guides the laser light guided by the coupling optical system 110 to the collimating optical system 130 provided at the subsequent stage. The light emitted from the optical fiber 120 becomes a rotationally symmetric beam, which contributes to uniform luminance distribution. The optical fiber 120 is not particularly limited, and a known multimode optical fiber (for example, a step index type multimode fiber) can be used. Also, the core diameter of the optical fiber 120 is not particularly limited, and for example, a core diameter of about 1 mm can be used.

  In the optical fiber 120 according to the present embodiment, light is guided to the incident end of the optical fiber 120 so that the numerical apertures between the plurality of light sources match at the incident end of the optical fiber as much as possible. At this time, by optimizing the focal length of the lens that collimates the laser light emitted from the laser light source, the laser light emitted from the emission end of the optical fiber 120 has a light quantity near the central optical axis of the optical fiber. It is desirable that the light beam is not a donut-shaped light beam that is lower than the light amount in the peripheral portion, but is a solid light beam in the vicinity of the central optical axis of the optical fiber having a light amount equivalent to that in the peripheral portion.

  The collimating optical system 130 is provided on the downstream side of the emission end of the optical fiber 120 and converts the laser light emitted from the optical fiber 120 into a parallel light beam. By converting the laser light into a parallel light beam by the collimating optical system 130, the diffusion state of the laser light can be easily controlled by the diffusion angle of the diffusion member 140 in the diffusion member 140 provided in the subsequent stage. . The configuration of the collimating optical system 130 is not particularly limited, and a known optical system for converting laser light into a parallel light beam may be configured by appropriately combining known optical elements.

  The diffusing member 140 is provided in the vicinity of the rear focal position of the collimating optical system 130, and generates a secondary light source by diffusing the parallel light beam emitted from the collimating optical system 130. That is, the light emission end of the diffusing member 140 functions as a secondary light source.

  The size of the secondary light source generated by the diffusing member 140 can be controlled by the focal length of the collimating optical system 130. Further, the NA of the emitted light can be controlled by the diffusion angle of the diffusion plate. Due to both effects, it is possible to increase the invariant of the Lagrange expressed by Equation 2 above, and to achieve both a desired light source size and a desired illumination range.

  If the size of the secondary light source is to be adjusted, the size of the secondary light source may be optimized based on the NA emitted from the optical fiber and the focal length of the collimating optical system. The actual range of the vicinity of the rear focal position is not particularly limited, but includes, for example, the focal distance ± 10% on the upstream side and the downstream side including the rear focal position. It is preferable to be within a range.

  The divergence angle of light emitted from the diffusing member 140 is controlled by the diffusion angle of the diffusing member 140. Now, the outgoing angle when a parallel light beam having an angle of view ω (degrees) is transmitted through a diffusing member (for example, a diffusing plate) is approximated by Equation 101 below.

Here, in Equation 101 above,
Θ: Diffusing member exit angle Θ _w : angle of view of incident light Θ _d : diffusion angle of the diffusing member.

Now, it is assumed that the diffusion angle Θ _d of the diffusion member is 23 degrees and the core diameter w of the optical fiber 120 (multimode fiber) is 1 mm. The angle of view Θ _w of the incident light is given by Θ _w = atan {(w / 2) / f _col } when the focal length of the collimating optical system 130 is f _col , for example, the focal length of the collimating optical system is For reference, if f _col = 7.9 mm, Θ _w = 3.6 degrees. Substituting these Θ _d and Θ _w into the above equation 101 yields the exit angle Θ of the diffusion member = 23.27 degrees. As a result, if the core diameter of the multimode fiber is about the above at the exit angle Θ of the diffusing member, the angle of view Θ _w has little effect, and both on-axis and off-axis light is diffused. It shows that the diffusion angle is set to 140.

In the present embodiment, the diffusion angle of the diffusing member 140 is not particularly limited, and is appropriately determined according to the size to be realized by the lighting device 1 and the characteristic values of the diffusing member applicable to the lighting device 1. That's fine. The diffusion angle Θ _d can be set to about 23 degrees, for example.

  The specific type of the diffusing member 140 is not particularly limited, and a known diffusing element can be used. As an example of such a diffusing member, for example, an opal type diffusing plate or a holographic diffusing plate utilizing diffusion characteristics by dispersing a light diffusing substance in frosted ground glass or glass can be cited. The holographic diffusion plate is particularly preferable because a holographic pattern is formed on a predetermined substrate, and a diffusion angle of emitted light can be set to an arbitrary angle.

  The light emitted from the diffusing member 140 is guided to the condenser optical system 150. The condenser optical system 150 forms an image of the secondary light source formed on the diffusing member 140 onto the illumination target with a predetermined paraxial lateral magnification. Examples of the illumination target include an incident end of a light guide provided in the endoscope unit, which is located on the downstream side of the condenser optical system 150. As schematically shown in FIG. 1B, at the incident end of the light guide, a plurality of optical fibers composed of a fiber core portion and a fiber cladding portion are bundled. Here, unlike the conventional case, the condenser optical system 150 according to the present embodiment connects the secondary light source so as to fill the area of the illumination target (for example, the entrance end of the ride guide provided in the endoscope unit) as much as possible. Let me image. Thereby, speckle noise can be reduced as the entire lighting device 1.

  The imaging magnification (paraxial lateral magnification) β of the condenser optical system 150 is expressed by the following formula 102 by the focal length f of the condenser optical system and the distance X from the focal position F to the object plane.

    β = f / X (Formula 102)

  Here, when the condenser optical system 150 has no aberration, the imaging magnification β of the condenser optical system 150 and the incident numerical aperture and the outgoing numerical aperture of the condenser optical system 150 satisfy the relational expression represented by the following expression 103. .

β = Y ′ / Y = NA _cond / NA _{cond ′} (Formula 103)
Y: size of secondary light source Y ′: size of image of secondary light source NA _cond : entrance numerical aperture of condenser optical system NA _{cond ′} : exit numerical aperture of condenser optical system

On the other hand, the allowable numerical aperture NA _L of the light guide is a bundle fiber that bundles the optical fibers, the refractive index of the core portion of the optical fiber and n _1, the refractive index of the cladding portion is taken as n _2, the following formula 104, the allowable numerical aperture NAL of a typical light guide is in the range of 0.56 ≦ NA _L ≦ 0.88.

  Further, in order to condense light from the light source by the condenser optical system 150 and efficiently enter the light guide provided at the subsequent stage of the condenser optical system 150, it is preferable to satisfy the relationship of the following expression 105.

NA _{cond ′} ≦ NA _L (Formula 105)

In addition, in the illumination device 1 according to the present embodiment, the diameter of the incident end of the light guide on which the secondary light source transmitted through the condenser optical system 150 enters is φ _LG, and the size of the image of the secondary light source is Y ′. Then, it is preferable that the size of the image of the secondary light source is controlled so that the relationship represented by the following formula 106 is established. That is, it is desirable that the image of the secondary light source fills the incident end of the light guide. By satisfying the relational expression expressed by the following expression 106, it is possible to reduce speckle noise while satisfying the relational expression expressed by the above expression 105. Note that the size of the image of the secondary light source is defined by the emission NA of the multimode fiber and the focal length of the collimator.

0.8 ≦ Y ′ / φ _LG ≦ 1.2 (Formula 106)

When Y ′ / φ _LG is less than 0.8, the image of the secondary light source is smaller than the diameter of the incident end of the light guide. The light guide entrance and exit ends are generally conjugated, and as a result, when illuminated with light guide exit light, the apparent light source size when viewed from the irradiated surface is reduced, and speckle deteriorates. End up. When the secondary light source is controlled so as to be sufficiently smaller than the core diameter from the viewpoint of optical coupling efficiency, there is a high possibility that speckle will deteriorate when the spot size is small. In addition, in the case of an endoscope configured to divide the light guide halfway and illuminate with a plurality of emission ends, the luminance distribution between the branched emission ends is greatly different, and there is a problem that speckle is deteriorated.

On the other hand, when Y ′ / φ _LG exceeds 1.2, the secondary light source or the image of the secondary light source becomes larger than the diameter of the incident end of the light guide. In that case, vignetting of the laser light occurs on the light guide incident end face, and the optical coupling efficiency is lowered.

The diameter φ _LG of the incident end of the light guide where the image of the secondary light source formed by the condenser optical system is formed and the size Y ′ of the image of the secondary light source are related by Y ′ = φ _LG Is more preferable.

  Further, the paraxial lateral magnification β of the condenser optical system 150 may be determined as appropriate so that the image size Y ′ of the secondary light source satisfies the range of the above formula 106, but 0.4 ≦ β ≦ 2. 3 is more preferable.

  When the paraxial lateral magnification β is less than 0.4, the effective diameter of the diffusing member 140 becomes too large, and the apparatus may be increased in size, which is not preferable. On the other hand, when the paraxial lateral magnification β exceeds 2.3, a large diffusion angle is required for the diffusing member 140, and the transmittance may be reduced. In addition, a special structure as the diffusing member 140 must be obtained separately, which may increase the cost. When the paraxial lateral magnification β of the condenser optical system 150 falls within the above range, it is possible to reduce the size of the apparatus while suppressing the cost for manufacturing the illumination apparatus. Further, as a method of adjusting the image size Y ′ of the secondary light source so as to satisfy Expression 106, a mechanism that can adjust the interval between the condenser lens and the incident end face of the light guide may be provided.

  The configuration of the lighting device 1 according to this embodiment has been described in detail above with reference to FIGS. 1A and 1B.

[Specific examples of lighting devices]
Next, the configuration of the illumination device according to the present embodiment will be specifically described with reference to FIGS.

  FIG. 2 schematically illustrates the configuration of the illumination device 1 when a laser light source that emits red light, green light, and blue light is used as the laser light source 100 and a holographic diffusion plate 141 is used as the diffusion member 140. It is shown. FIG. 3 schematically shows a configuration of the illumination device 1 when a laser light source that emits red light, green light, and blue light is used, and the microlens array 143 is used as the diffusing member 140.

  As shown in FIGS. 2 and 3, the laser beams emitted from the RGB laser light sources are combined by the mirror M and the dichroic mirror DM and guided to the collector lens L. As shown in FIGS. 2 and 3, when a plurality of lasers are used as light sources, for example, as schematically shown in FIG. 4, the beam diameter of each color is different at the pupil position of the collector lens L. Can occur.

  As described above, when RGB colors are coupled to the optical fiber 120 by the collector lens L, it is preferable that the numerical apertures incident on the optical fibers of the respective colors are uniform. The reason for this is as follows. Generally, since the lens power arrangement is determined in accordance with the laser beam having the largest incident numerical aperture, the laser beam having a small incident numerical aperture has a small beam diameter at the diffuser plate position. That is, the luminance distribution at the light guide incident end becomes non-uniform. In order to align the incident numerical aperture of each color, for example, there is a method of matching the apparent beam diameter of each color at the pupil position of the collector lens L. In this method, for example, as schematically shown in FIG. 5, the end of the laser beam with the smallest beam diameter is located at the position where the maximum numerical aperture is reached (that is, the end of the laser beam with the largest beam diameter). What is necessary is just to make it locate. By doing so, the laser beam with the largest beam diameter and the laser beam with the smallest beam diameter come into contact with each other at a certain point. In FIG. 5, the two laser beams are in contact with each other at the end on the positive side of the ξ axis. However, the position is not limited to the case shown in FIG. The ends may be in contact with each other.

  Further, when multiple lasers having the same or near wavelengths are multiplexed for reasons such as securing output or reducing temporal coherence, as schematically shown in FIG. 6, at least the center of the pupil, What is necessary is just to arrange | position a beam with the smallest beam diameter in the position of the largest incident numerical aperture.

  As shown schematically in FIGS. 5 and 6, by matching the incident numerical apertures, the light quantity distribution of the secondary light source formed at the position of the diffusing member 140 is made uniform, and the difference in speckle generation amount due to color. Can be reduced. In other words, the maximum beam diameters of the secondary light sources of the respective colors formed on the diffusing member 140 are substantially equivalent, and the difference in speckle generation amount due to colors can be reduced.

  In order to realize the situation shown in FIG. 5, a dichroic mirror DM provided as one of the coupling optical systems 110 is used as a numerical aperture adjusting unit, and the incident position of the laser light on the collector lens L is adjusted. do it.

  Specifically, as shown in FIG. 7, when there is a laser light source A that emits laser light with a larger beam diameter and a laser light source B that emits laser light with a smaller beam diameter, the coupling optical system 110 The beam position may be offset as shown in FIG. 5 by shifting the dichroic mirror DM with respect to the central optical axis in the direction of the optical axis. Thereby, as shown in FIG. 5, it is possible to align the beam positions with each other.

  FIG. 8 shows a result of actually shifting the dichroic mirror with such a configuration. The horizontal axis in FIG. 8 indicates the shift amount of the dichroic mirror DM with respect to the central optical axis of the coupling optical system 110, and the vertical axis in FIG. 8 indicates the speckle contrast ratio (SCR) corresponding to the speckle amount. Yes. As is clear from FIG. 8, it can be seen that the luminance distribution at the light guide incident end approaches uniformly due to the shift, and the speckle contrast is reduced.

  In order to realize the situation shown in FIG. 6, for example, as shown in FIGS. 9A and 9B, as the numerical aperture adjusting unit, a mirror M, a λ / 2 wavelength plate, a polarizing beam splitter PBS Further, the incident position of the laser beam on the dichroic mirror DM may be adjusted by further utilizing the above.

  For a laser light source that emits a laser beam having a large beam diameter, the paraxial lateral magnification of the condenser optical system 150 is set so as to satisfy the above formula 106 without providing such a numerical aperture adjustment unit, and the beam diameter is small. With respect to the laser light source that emits laser light, it is possible to realize a mode in which the numerical aperture is adjusted so as to satisfy the above-described formula 106 by using the numerical aperture adjusting unit.

  The configuration of the lighting device according to the present embodiment has been specifically described above with reference to FIGS.

<About the configuration of the endoscope>
Next, a configuration of the endoscope 10 in which the illumination device 1 according to the present embodiment is used as an illumination light source will be briefly described with reference to FIG. FIG. 10 is an explanatory diagram schematically illustrating the configuration of an endoscope including the illumination device according to the present embodiment.

  The illumination device 1 as described above is used as a light source, and an image of the light source by the condenser optical system is formed on a light guide 901 provided in an arbitrary endoscope unit 900, thereby reducing illumination light with reduced speckle noise. Can be obtained. The illumination light guided to the light guide 901 is guided to the endoscope body 903 by the light guide 901 and guided to the distal end portion of the endoscope.

Here, the endoscope unit 900 to which the illumination device 1 is attached is not particularly limited, and any endoscope unit 900 including a general light guide 901 can be used. is there. Conversely, if you want to use the endoscope unit 900 having a certain light guide 901, in response to the allowable incident numerical aperture NA _L of the light guide 901, the secondary light source image of the illumination device 1 according to this embodiment Y ′ and the paraxial lateral magnification β of the condenser optical system 150 may be set.

  The endoscope 10 including the illumination device 1 according to the present embodiment has been briefly described above with reference to FIG.

<Specific example of condenser optical system>
Next, the condenser optical system 150 in the illumination device 1 according to this embodiment will be described with reference to FIGS. 11 to 12C with specific examples. FIG. 11 is an explanatory diagram illustrating lens data of the condenser optical system according to the present embodiment, and FIGS. 12A to 12C are explanatory diagrams illustrating lens configuration examples of the condenser optical system according to the present embodiment.

  Specific lens data of the condenser optical system 150 according to the present embodiment is shown in FIG. 11, and lens configuration diagrams are shown in FIGS. 12A to 12C. In the table shown in FIG. 11, f is the focal length, S1toH is the distance from the first surface of the condenser lens system to the front principal point position, β is the paraxial lateral magnification, and OBJ is The distance from the first surface to the object surface, and X is the distance from the focal position F to the object surface. In the table shown in the upper part of FIG. 11, the lens data of the columns A to C correspond to the lens configuration diagrams shown in FIGS. 12A to 12C, respectively.

The condenser optical system 150 shown in FIGS. 11 to 12C assumes a case where a light guide 901 having a light guide incident surface diameter φ _LG = 2.0 and an allowable numerical aperture NA _L = 0.57 is used. The other setting values of the lighting device 1 are as follows.

Multimode fiber exit numerical aperture NA _M = 0.22
Collimating optical system focal length f _col = 7.6
Secondary light source size Y = 3.34
Diffuser angle = 23 degrees

  As shown in FIGS. 12A to 12C, each specific example of the condenser optical system 150 according to this embodiment includes an incident surface on the secondary light source side (a surface located on the right side in the drawings in FIGS. 12A to 12C), In addition, the image-side emission surface of the secondary light source (the surface located on the left side in the drawings in FIGS. 12A to 12C) includes a lens system that is a flat surface. Further, as is apparent from the table shown in the lower part of FIG. 11 and FIGS. 12A to 12C, the condenser optical system 150 includes a positive plano-convex lens having a plane facing the diffusion member side in order from the diffusion member 140 side. The lens system includes one or more positive lenses and a positive plano-convex lens having a plane directed to the rear stage side of the condenser optical system 150. The surface of the plano-convex lens located closest to the image side of the secondary light source on the diffusing member 140 side (corresponding to surface number S = 7 in the lens data shown in the lower part of FIG. 11) is an aspherical surface. ing.

  A rotationally symmetric aspherical surface with the optical axis as the center is represented by the following expression 107. Here, in the following expression 107, C is a curvature (1 / r), h is a height from the optical axis, and K is a cone coefficient. Further, the aspheric surface data of the surface number S = 7 is as shown in the lower part of FIG.

  In the condenser optical system 150 according to the present embodiment, it is possible to reduce the cost by using a lens as shown in FIGS.

  In particular, in the case of the lens configuration shown in FIG. 12B, since β = 0.6 and Y = 3.34, Y ′ = 2 and Expression 106 is satisfied. In addition, NA = 0.57, and Expression 105 is also established, and it is possible to couple the illumination light to the light guide with high efficiency. Even in an illumination optical system using a laser with a small Lagrangian invariant as a light source, it is possible to achieve both a large light source size and a large divergence angle required when coupled to a light guide by this optical system. It becomes possible.

  The illumination device, illumination method, and endoscope according to the first embodiment of the present invention have been described in detail above with reference to FIGS. 1 to 12C.

(Second Embodiment)
Hereinafter, an illuminating device and an illuminating method capable of reducing speckle noise of laser light emitted from a light source, and an endoscope having the illuminating device will be described in detail.

<About the configuration of the lighting device>
First, the configuration of the illumination device according to the second embodiment of the present disclosure will be described with reference to FIGS. 13A to 19. FIG. 13A to FIG. 17 and FIG. 19 are explanatory diagrams schematically showing the configuration of the illumination device according to the second embodiment of the present disclosure. 18A and 18B are explanatory diagrams for explaining the positional relationship between the pupil position of the collector lens and the laser beam.

  The illumination device 2 according to the present embodiment includes at least a laser light source 200, an optical fiber 220, and a diffusion member 240, as schematically shown in FIG. 13A. Further, as schematically shown in FIG. 13B, the illumination device 2 according to the present embodiment further includes a coupling optical system 210 between the laser light source 200 and the optical fiber 220, and the optical fiber 220 and the diffusing member 240. It is preferable to further have a collimating optical system 230 between the two.

  At least one laser light source 200 is provided in the illumination device 2 and emits laser light having a predetermined wavelength. In the illuminating device 2 according to the present embodiment, as the laser light source 200, various semiconductor lasers and solid-state lasers can be used, and a combination of these lasers and a wavelength conversion mechanism can also be used. Is possible. The wavelength of the laser light emitted from the laser light source 200 may be appropriately selected according to what kind of object or phenomenon is observed in the illumination target. Examples of such a wavelength include a visible light band having a wavelength of about 400 to 700 nm and a near infrared band used for ICG (Indocyanine green) fluorescence imaging. When such laser light is used as excitation light for fluorescence excitation, the observed fluorescence may include autofluorescence at the excitation light irradiation site, drug fluorescence due to various fluorescent reagents introduced into the irradiation site, and the like. .

  The coupling optical system 210 is an optical system for optically coupling the laser light emitted from the laser light source 200 to the optical fiber 220 provided in the subsequent stage. The configuration of the coupling optical system 210 is not particularly limited, and various known optical elements may be appropriately combined so that the laser beam is optically coupled to the optical fiber 220. The laser beam can be coupled to the optical fiber. At least one condenser lens (collector lens) for optical coupling to 220 is provided.

  In addition, the coupling optical system 210 further includes a collimating lens between the laser light source 200 and the collector lens, which makes the laser light emitted from the laser light source 200 substantially parallel (in other words, a substantially parallel light beam). It is preferable. Here, “substantially parallel” means that the radiation angle of the light emitted from the collimating lens is minimized, and the position of the focal length of the collimating lens and the beam of the laser light emitted from the laser light source 200. Achieved when matching the waist position.

  Furthermore, in the case of realizing white illumination light by combining a plurality of laser light sources 200 such as a red semiconductor laser, a green light emitting semiconductor excitation solid-state laser, and a blue reaction laser, the coupling optical system 210 includes, in addition to the collector lens, At least one dichroic mirror or dichroic prism is further provided. The plurality of laser beams emitted from the plurality of laser light sources 200 are combined by a dichroic mirror or a dichroic prism to generate white light. The combined light is collected by the collector lens and coupled to the optical fiber 220.

  Here, in the illumination device 2 according to the present embodiment, the laser light is incident on the incident end face of the optical fiber 220 from an oblique direction with respect to the normal line of the incident end face. More specifically, when the condensing angle or emission angle of the laser light (or the combined light) is smaller than the numerical aperture (that is, the allowable incident angle) of the optical fiber 220, the laser light is The laser beam is angled within a numerical aperture (allowable incident angle) of 220 and is incident from an oblique direction with respect to the normal of the incident end face. Even more preferably, the illumination device 2 according to the present embodiment includes the normal direction of the incident end face in the angle component at the incident end face of the laser light. Thereby, speckle noise of the laser light emitted from the laser light source 200 can be reduced. Note that how laser light is incident on the optical fiber 220 will be described in detail later.

  The optical fiber 220 guides the laser light guided by the coupling optical system 210 to the diffusion member 240 shown in FIG. 13A or the collimating optical system 230 shown in FIG. The optical fiber 220 is not particularly limited, and a known multimode optical fiber (for example, a step index type multimode fiber) can be used. Further, the core diameter of the optical fiber 220 is not particularly limited, and for example, a core having a core diameter of about 1 mm can be used.

  In the optical fiber 220 according to this embodiment, the laser light is guided from an oblique direction with respect to the normal of the incident end face so that the incident angle is as large as possible within the allowable numerical aperture of the optical fiber. The radiation angle of the laser light emitted from the exit end of the fiber 220 is larger than the condensing angle of the laser light at the entrance end face.

  In the far-field image (intensity distribution) of the laser light emitted from the exit end of the optical fiber 220, when the incident angle component of the laser light incident on the optical fiber 220 does not include the normal direction of the entrance end face, the optical fiber The donut shape is such that the amount of light in the vicinity of the center optical axis is lower than the amount of light in the peripheral portion. On the other hand, when the normal angle direction of the incident end face is included in the incident angle component of the laser light incident on the optical fiber 220, the solid shape is such that the vicinity of the central optical axis of the optical fiber has the same amount of light as the peripheral portion. . Accordingly, in the illumination device 2 according to the present embodiment, more preferably, the laser beam emitted from the emission end of the optical fiber 220 includes the normal direction of the incident end surface in the incident angle component of the laser light incident on the optical fiber 220. The far-field image (intensity distribution) of light is configured to have a solid shape.

  The collimating optical system 230 is provided on the downstream side of the emission end of the optical fiber 220 and makes the laser light emitted from the optical fiber 220 substantially parallel. By substantially collimating the laser light emitted from the optical fiber 220 by the collimating optical system 230, the diffusion state of the laser light can be easily controlled by the diffusion angle of the diffusion member 240 in the diffusion member 240 provided in the subsequent stage. Is possible. The configuration of the collimating optical system 230 is not particularly limited, and a known optical system for converting laser light into a parallel light beam may be configured by appropriately combining known optical elements.

  The diffusing member 240 is provided in the subsequent stage of the optical fiber 220 (after the collimating optical system 230 when the collimating optical system 230 is provided), and the laser beam emitted from the optical fiber 220 or the collimating optical system 230 is transmitted. By diffusing, a secondary light source is generated. That is, the light emission end of the diffusing member 240 functions as a secondary light source.

  Here, the divergence angle of the light emitted from the diffusion member 240 is controlled by the diffusion angle of the diffusion member 240 as described in the first embodiment.

  In the present embodiment, the diffusion angle of the diffusing member 240 is not particularly limited, and is appropriately determined according to the size to be realized by the illuminating device 2, the characteristic value of the diffusing member applicable to the illuminating device 2, and the like. That's fine.

  The specific type of the diffusing member 240 is not particularly limited, and a known diffusing element can be used. Examples of such diffusing members include, for example, frosted ground glass and diffusing plates such as opal diffusing plates, holographic diffusing plates, and microlens arrays that utilize diffusion characteristics by dispersing a light diffusing material in the glass. In addition, a bundle fiber in which a plurality of optical fibers are bundled can be given. The holographic diffusion plate is obtained by applying a holographic pattern on a predetermined substrate, and the diffusion angle of emitted light can be set to an arbitrary angle. The microlens array can set the diffusion angle of the emitted light to an arbitrary angle. Note that the diffusion effect by the bundle fiber is limited. For light incident at an angle θ with respect to the normal of the incident end face, the outgoing beam is scattered into a cone shape having an angle θ with respect to the normal of the outgoing end face. Is done.

  The configuration of the illumination device 2 according to the present embodiment has been described in detail above with reference to FIGS. 13A and 13B.

[Specific examples of lighting devices]
Next, the configuration of the illumination device according to the present embodiment will be specifically described with reference to FIGS. 14A to 19.

In the case where there is one laser light source First, the case where one laser light source is used as the laser light source 200 will be described as an example with reference to FIGS. 14A to 15.

  Laser light emitted from one laser light source 200 is guided to a collimating lens CL provided as a coupling optical system 210 and is substantially parallelized to become a parallel light flux. The laser light that has become a parallel light beam is guided to the collector lens L. The collector lens L optically couples the incident parallel light beam to the multimode single core optical fiber 220. Here, the central optical axes of the laser light source 200, the collimating lens CL, and the collector lens L at the incident end face of the optical fiber 220 are relative to the optical axis of the optical fiber 220 (in other words, the normal line of the incident end face of the optical fiber 220). The light is incident from an oblique direction. The angle between the two optical axes is θ. By causing the laser light to enter the incident end face of the optical fiber 220 from an oblique direction, speckle noise caused by the laser light source 200 can be reduced.

Now, as shown in FIG. 14B, when the condensing angle of the laser light at the incident end face of the optical fiber 220 is θ _beam, and as shown in FIG. 14C, the allowable incident angle of the optical fiber 220 is θ _fiber , In the illumination device 2 according to the present embodiment, it is preferable for speckle reduction that the relationship represented by the following Expression 201 and Expression 201-2 is satisfied. Here, it is assumed that θ _beam <θ _fiber .

(Θ + θ _beam ) ≦ θ _fiber (Formula 201)
θ ≦ θ _beam (Formula 201-2)

  By satisfying the relationship represented by the above equation 201, the laser light propagates through the optical fiber 220 without loss, and by selecting a larger θ, the laser light emitted from the optical fiber 220 has a more radiation angle. growing.

  Further, when the relationship represented by the above expression 201-2 is satisfied, the angle component of the laser light incident on the optical fiber 220 includes the normal direction of the incident end surface, and is emitted from the exit end of the optical fiber 220. The far-field image (intensity distribution) of the laser light has a solid shape, not a donut shape.

In the above formula 201, (θ + θ _beam ) = θ _fiber is more preferable. In this case, θ is the maximum value, and the maximum radiation angle corresponding to the allowable incidence angle of the optical fiber 220 is obtained. Further, the relationship represented by (θ + θ _beam ) = θ _fiber is realized at the same time as the expression 201-2, so that the laser beam emitted from the optical fiber 220 has a maximum radiation angle and a solid far-field image (intensity). Distribution).

  The laser light guided by the optical fiber 220 is emitted from the emission end of the optical fiber 220 and guided to the diffusion member 240. The diffusing member 240 projects a beam from the optical fiber 220 to form a secondary light source on the diffusing surface on the diffusing member 240 (the emission end surface of the diffusing member 240). The intensity distribution (or beam size) on the diffusion surface of the secondary light source is equal to the intensity distribution (or beam size) formed by the light from the optical fiber 220 on the diffusion surface. Light from the secondary light source is emitted to the observation field and illuminates the illumination target. In addition, when using this illuminating device 2 as a light source for endoscopes, in order to obtain a high viewing angle, the radiation angle of a secondary light source is often increased, and a diffusion member having a large diffusion angle is selected.

  The speckle observed in the illumination object is reduced as the beam size of the secondary light source is larger and the shape is solid (uniform intensity distribution). Therefore, it is possible to further reduce speckle noise by satisfying the above-described equation 201 and selecting a larger θ. Furthermore, the speckle noise can be further reduced by satisfying the relationship represented by the expression 201-2.

  Moreover, in the illuminating device 2 which concerns on this embodiment, about FIGS. 14A-14C, about the case where the center optical axis of the laser light source 200, the collimating lens CL, and the collector lens L and the optical axis of the optical fiber 220 mutually cross | intersect. As shown in FIG. 15, the central axis of the parallel light flux of the laser light is shifted in parallel to the collector lens L and the optical axis composed of the collector lens L and the optical fiber 220. It may enter the position.

In this case, as shown in FIG. 15, the beam width of the parallel beam and W _A, the focal length of the collector lens L is f, the incidence acceptance angle of the optical fiber 220 and theta _fiber, collector lens L and the optical fiber 220 when the amount of shift from the center of the optical axis was D _a consisting of the following formulas 202, it is that the relationship of formula 202-2 is established, preferably to the speckle reduction. However, here, it is assumed that (W _A / 2) <(f × sin (θ _fiber )).

(W _A / 2) + D _A ≦ (f × sin (θ _fiber )) (Formula 202)
D _A ≦ (W _A / 2) (Formula 202-2)

By relation represented by the above formula 202 are satisfied, the optical fiber 220 propagates laser light without loss, and, by selecting a larger D _A, more radiation angle laser light emitted from the optical fiber 220 Becomes larger.

  Further, when the relationship represented by the above expression 202-2 is satisfied, the angle component of the laser light incident on the optical fiber 220 includes the normal direction of the incident end surface, and is emitted from the exit end of the optical fiber 220. The far-field image (intensity distribution) of the laser light has a solid shape, not a donut shape.

In the above formula 202, (W _A / 2) + D _A = (f × sin (θ _fiber )) is more preferable. In this case, the maximum radiation angle corresponding to the allowable incidence angle of the optical fiber 220 is obtained. In addition, since the relationship represented by (W _A / 2) + D _A = (f × sin (θ _fiber )) is realized simultaneously with the expression 202-2, the laser light emitted from the optical fiber 220 has the maximum radiation. It becomes a far-field image (intensity distribution) of a corner and a solid shape.

  The laser light guided by the optical fiber 220 is emitted from the emission end of the optical fiber 220 and guided to the diffusion member 240. The diffusing member 240 projects a beam from the optical fiber 220 to form a secondary light source on the diffusing surface on the diffusing member 240 (the emission end surface of the diffusing member 240). The intensity distribution (or beam size) on the diffusion surface of the secondary light source is equal to the intensity distribution (or beam size) formed by the light from the optical fiber 220 on the diffusion surface. Light from the secondary light source is emitted to the observation field and illuminates the illumination target. In addition, when using this illuminating device 2 as a light source for endoscopes, in order to obtain a high viewing angle, the radiation angle of a secondary light source is often increased, and a diffusion member having a large diffusion angle is selected.

The speckle observed in the illumination object is reduced as the beam size of the secondary light source is larger and the shape is solid (uniform intensity distribution). Therefore, satisfying the equation 202, and, by selecting a larger D _A, it is possible to further reduce the speckle noise. Furthermore, the speckle noise can be further reduced by satisfying the relationship represented by the expression 202-2.

  As shown in FIG. 16, a collimating lens (that is, a collimating optical system) 230 may be disposed between the optical fiber 220 and the diffusing member 240. FIG. 16 shows a case where the central axis of the parallel light flux of the laser light is incident on the collector lens L at a position that is parallel to the optical axis composed of the collector lens L and the optical fiber 220 and shifted. Although shown, it goes without saying that the collimating optical system 230 may be similarly disposed even when the laser light is incident on the incident end face of the optical fiber 220 from an oblique direction.

Case where there are a plurality of laser light sources Next, a case where a plurality of laser light sources are used as the laser light source 200 will be described with reference to FIGS.

  Hereinafter, a case where white light is realized using a red laser light source (Red) that emits red laser light, a green laser light source (Green), and a blue laser light source (Blue) will be described.

  As shown in FIG. 17, the red laser light emitted from the red laser light source is converted into a parallel light beam by the collimator lens CL, reflected by the mirror M, and transmitted through the two dichroic mirrors DM, while being collected by the collector lens. L is guided to L.

  The green laser light emitted from the green laser light source is converted into a parallel light beam by the collimating lens CL, then reflected by the dichroic mirror DM, and guided to the collector lens L while passing through the dichroic mirror DM for blue laser light. Lighted.

  The blue laser light emitted from the blue laser light source is converted into a parallel light beam by the collimating lens CL, then reflected by the dichroic mirror DM, and guided to the collector lens L.

  Now, as shown in FIG. 17, the optical axis of the red laser light is C1, the optical axis of the green laser light is C2, and the optical axis of the blue laser light is C3. The optical axis C1 of the red laser light is disposed so as to be coaxial with the mirror M, the dichroic mirror DM, the collector lens L, and the optical axis C0 of the optical fiber 220.

  FIG. 18A shows an example of beam arrangement in the AA cross section of FIG. In FIG. 18A, the beam cross section of the laser light source 200 (primary light source) is assumed to be a perfect circle. Here, the beam with the maximum beam width is arranged so that the beam center axis C1 coincides with the center optical axis C0. In FIG. 18A, the beam with the maximum beam width is a red beam, and the beam width is W1. It is said that. That is, in FIG. 18A, the beam width of each laser beam is W1> W2 and W1> W3.

  In FIG. 18A, the beam width of the red beam is selected in a range that transmits through the collector lens L and the optical fiber 220 in the subsequent stage. That is, when the permissible transmission beam width determined by the collector lens L and the optical fiber 220 is W0, the relationship is W0> W1.

  In FIG. 18A, the allowable beam width is indicated by W 0, and the beam (laser light) traveling inside the allowable outer circumference of the radius R 0 shaped by the beam width W 0 can pass through the optical fiber 220. Note that the shape of the allowable outer circumference circle is a shape determined by the collector lens L and the optical fiber 220. When a lens that is rotationally symmetric with respect to the normal optical axis center C0 is used as the collector lens L, W0 is a radius. It becomes a perfect circle shape of R0 = W0 / 2.

  Here, as shown in FIGS. 17 and 18A, the respective beam center positions (that is, C2 and C3) of the green and blue primary light source beams that are narrower than the maximum beam width do not coincide with C0, but are green and blue. The primary light source beam is arranged so as to be translated with respect to the central optical axis C0.

  The range of translation of the green and blue primary light source beams is within the circle (maximum outer circle of the beam) indicated by the maximum radius (R1 = W1 / 2 in FIG. 18A) formed by the red primary light source beam. It is set so that the blue primary light source beam is located. That is, if the distance of the green primary light source beam from the central optical axis C0 is D2, the range of D2 is 0 <D2 ≦ (R1-W2 / 2). Similarly, assuming that the distance of parallel movement of the blue primary light source beam is D3, the range of D3 is similarly 0 <D3 ≦ (R1−W3 / 2).

  Here, in the illuminating device 2 according to the present embodiment, in the cross section orthogonal to the optical axis as shown in FIG. 18A, the circle with the maximum radius centered on C0 formed by the maximum beam width (the maximum outer periphery of the beam). The remaining beam is preferably inscribed in the circle (at point P and point Q in FIG. 18A).

  In the example shown in FIG. 17A, it is preferable that the primary light source beams of green and blue are arranged so as to be inscribed in the maximum outer circumference of the beam indicated by R1. That is, the parallel movement distance D2 of the green primary light source beam is D2 = (R1-W2 / 2), and the parallel movement distance D3 of the blue primary light source beam is D3 = (R1-W3 / 2). is there.

  In FIG. 18A, preferably, the green and blue primary light source beams having a narrow beam width are arranged so that the beam exists in a radius of 0 to R1 centered on C0. Good. That is, W2 ≧ (W1 / 2) and W3 ≧ (W1 / 2), and the primary light source beams of red, green, and blue each include the optical axis center C0.

  This prevents a decrease in luminance at the center position in a hyperopic image of light emitted from the output end of the optical fiber 220 (that is, in the light intensity distribution at the diffusing member 240 in the optical system of FIG. 17). This is because of the shape.

  The laser light guided by the optical fiber 220 is emitted from the emission end of the optical fiber 220 and guided to the diffusion member 240. The diffusing member 240 projects a beam from the optical fiber 220 to form a secondary light source on the diffusing surface on the diffusing member 240 (the emission end surface of the diffusing member 240). The intensity distribution (or beam size) on the diffusion surface of the secondary light source is equal to the intensity distribution (or beam size) formed by the light from the optical fiber 220 on the diffusion surface.

  With the above operation, the primary light source beams of red, green, and blue have the same intensity distribution (or beam size) on the diffusing surface in the secondary light source, so speckle noises observed on the illumination target in each color (wavelength) Can be made equal to each other.

  FIG. 18B shows another example of beam arrangement in the AA cross section of FIG. In the example shown in FIG. 18B, the cross-sectional shape of each primary light source beam is an elliptical shape.

  Also in the example shown in FIG. 18B, the center positions of the green and blue primary light source beams (that is, C2 and C3) narrower than the maximum beam width do not coincide with C0, and the green and blue primary light source beams Are arranged so as to be translated with respect to the central optical axis C0.

  Even in such a case, the range of translation of the primary light source beams of green and blue is within the maximum outer circumference of the beam centered on C0 indicated by the maximum radius (R1 = W1 / 2) formed by the primary light source beam of red. , Green and blue primary light source beams are disposed. As shown in FIG. 17B, each primary light source beam is preferably arranged so that the green and blue primary light source beams are inscribed in the maximum outer circumference of the beam centered on C0.

  Furthermore, it is preferable that the green and blue primary light source beams having a narrow beam width are arranged so that the beam exists in the radius 0 to R1 centered on C0. That is, each of the primary light source beams of red, green, and blue includes the optical axis center C0. This prevents a decrease in luminance at the center position in a hyperopic image of light emitted from the output end of the optical fiber 220 (that is, in the light intensity distribution at the diffusing member 240 in the optical system of FIG. 17). This is because of the shape.

  With the above operation, the primary light source beams of red, green, and blue have almost the same intensity distribution (or beam size) on the diffusion surface in the secondary light source, so speckle noises observed on the illumination target in each color (wavelength) Can be made equal to each other.

  Note that the parallel movement of the beam as shown in FIGS. 17 to 18B can be adjusted by the movement of the dichroic mirror DM as described in the first embodiment.

  As shown in FIG. 19, a collimating lens (that is, a collimating optical system) 230 may be disposed between the optical fiber 220 and the diffusing member 240.

  The configuration of the lighting device according to the present embodiment has been specifically described above with reference to FIGS. 17 to 19.

<About the configuration of the endoscope>
Next, the configuration of the endoscope 10 in which the illumination device 2 according to the present embodiment is used as an illumination light source will be briefly described with reference to FIG. FIG. 20 is an explanatory diagram schematically illustrating the configuration of an endoscope including the illumination device according to the present embodiment.

  By using the illumination device 2 as described above as a light source and combining the emitted secondary light source with a light guide 901 provided in an arbitrary endoscope unit 900, a photographed image with reduced speckle noise is obtained. It becomes possible. The illumination light from the secondary light source guided to the light guide 901 is guided to the endoscope body 903 by the light guide 901 and guided to the distal end portion of the endoscope.

  Here, the endoscope unit 900 to which the illumination device 1 is attached is not particularly limited, and any endoscope unit 900 including a general light guide 901 can be used. is there.

  Alternatively, the observation field may be illuminated with illumination light from the secondary light source by extending the optical fiber 220 of the light source device 2 to the distal end portion of the endoscope and installing the diffusion member 240.

  The endoscope 10 including the illumination device 2 according to the present embodiment has been briefly described above with reference to FIG.

<Verification example>
Hereinafter, with reference to FIG. 21 to FIG. 24, the speckle noise reduction degree is specifically described in the case of reducing speckle noise by translating the axis of the laser light source 200 (primary light source) from the optical axis. A verified example is shown.

  In the example shown in FIG. 21, a green light emitting semiconductor excitation solid-state laser is used as the laser light source 200. This laser is a laser light source from which a collimated beam is emitted. In FIG. 21, a primary light source beam with a beam width of 1 mm was formed by using a slit with a width of 1 mm. A step index type multimode fiber having a core diameter of 1 mm was used as the optical fiber 220, and the primary light source beam was condensed on the incident end face of the optical fiber 220 using a collector lens L having a focal length of 30 mm.

  A holographic diffusion plate was disposed as the diffusion member 240 at a position 5 mm from the emission end face of the optical fiber 220 to form a secondary light source for illuminating the illumination field. A test chart was placed at a position 300 mm from the secondary light source position, and speckles were measured by imaging the test chart with a CCD camera.

  In the example shown in FIG. 21, the optical axis center of the light incident on the collector lens L is moved by moving the dichroic mirror DM in the optical axis direction, and the speckle amount is measured at each moving position. The obtained measurement results are shown in FIG. The horizontal axis in FIG. 22 indicates the amount of deviation from the central optical axis C0 of the optical fiber 220, and the vertical axis in FIG. 22 indicates the speckle contrast ratio (SCR) corresponding to the speckle amount.

  As can be seen from the results shown in FIG. 22, the speckle amount decreases as the shift amount increases.

  In the example shown in FIG. 23, a bundle fiber is used as the diffusion member 240. As the laser light source 200, a green-emitting semiconductor-excited solid laser that emits a collimated beam was used. In the example shown in FIG. 23, a primary light source beam having a beam width of 1 mm was formed by using a slit having a width of 1 mm. A step index type multimode fiber having a core diameter of 1 mm was used as the optical fiber 220, and the primary light source beam was condensed on the incident end face of the optical fiber 220 using a collector lens L having a focal length of 30 mm.

  In addition, a bundle fiber having a bundle diameter of 5 mm was disposed as the diffusing member 240 at a position 10 mm from the emission end face of the optical fiber 220, and a secondary light source for illuminating the illumination field with the emission end face of the bundle fiber was formed. A test chart was placed at a position 300 mm from the secondary light position, and the test chart was imaged with a CCD camera to measure speckles.

  In the example shown in FIG. 23, the optical axis center of the light incident on the collector lens L is moved by moving the dichroic mirror DM in the optical axis direction, and the speckle amount is measured at each moving position. The obtained measurement results are shown in FIG. The horizontal axis in FIG. 24 indicates the amount of deviation from the center optical axis C0 of the optical fiber 220, and the vertical axis in FIG. 24 indicates the speckle contrast ratio (SCR) corresponding to the speckle amount.

  As is apparent from the results shown in FIG. 24, it can be seen that the speckle amount decreases as the shift amount increases.

(Third embodiment)
In the following, the method for reducing speckle noise of the entire lighting device described in the first embodiment and the speckle noise of laser light emitted from the light source described in the second embodiment are reduced. An example of a combination of the method and the method will be briefly described as a third embodiment.

<About the configuration of the lighting device>
First, the configuration of the illumination device according to the third embodiment of the present disclosure will be described with reference to FIG. FIG. 25 is an explanatory diagram schematically showing the configuration of the illumination device according to the present embodiment.

  As schematically shown in FIG. 25, the illumination device 3 according to the present embodiment includes a laser light source 300, a coupling optical system 310, an optical fiber 320, a collimating optical system 330, a diffusion member 340, and condenser optics. A system 350.

  At least one laser light source 300 is provided in the illumination device 3 and emits laser light having a predetermined wavelength. In the illuminating device 3 according to the present embodiment, various laser diodes and solid-state lasers can be used as the laser light source 300, and a combination of these lasers and a wavelength conversion mechanism can also be used. Is possible. The wavelength of the laser light emitted from the laser light source 300 may be appropriately selected according to what kind of object or phenomenon is observed in the illumination target. Examples of such a wavelength include a visible light band having a wavelength of about 400 to 700 nm and a near infrared band used for ICG (Indocyanine green) fluorescence imaging. When such laser light is used as excitation light for fluorescence excitation, the observed fluorescence may include autofluorescence at the excitation light irradiation site, drug fluorescence due to various fluorescent reagents introduced into the irradiation site, and the like. .

  The coupling optical system 310 is an optical system for optically coupling the laser light emitted from the laser light source 300 to the optical fiber 320 provided in the subsequent stage. The configuration of the coupling optical system 310 is not particularly limited, and various known optical elements may be appropriately combined so that the laser beam is optically coupled to the optical fiber 320. The laser beam can be coupled to the optical fiber. At least one condensing lens (collector lens) for optically coupling to 320 is provided.

  In addition, when the white illumination light is realized by combining a plurality of laser light sources 300, the coupling optical system 310 is further provided with at least one dichroic mirror or dichroic prism in addition to the collector lens. The plurality of laser beams emitted from the plurality of laser light sources 300 are combined by a dichroic mirror or a dichroic prism to generate white light. The combined light is collected by the collector lens and coupled to the optical fiber 320.

  When a plurality of laser light sources 300 are used in combination, it is preferable that the numerical apertures of the laser beams incident on the optical fiber 320 are uniform. However, since the FFP of each laser is different, it is actually difficult to align. Therefore, in such a case, the numerical aperture adjustment unit is provided in the coupling optical system 310 by the method as shown in the first embodiment and the second embodiment.

  The optical fiber 320 guides the laser light guided by the coupling optical system 310 to the collimating optical system 330 provided in the subsequent stage. The light emitted from the optical fiber 320 becomes a rotationally symmetric beam, which contributes to uniform luminance distribution. The optical fiber 320 is not particularly limited, and a known multimode optical fiber (for example, a step index type multimode fiber) can be used. Also, the core diameter of the optical fiber 320 is not particularly limited, and for example, a core diameter of about 1 mm can be used.

  In the optical fiber 320 according to the present embodiment, the light is guided to the incident end of the optical fiber 320 so that the numerical apertures between the plurality of light sources coincide as much as possible at the incident end of the optical fiber. At this time, by optimizing the focal length of the lens that collimates the laser light emitted from the laser light source, the laser light emitted from the emission end of the optical fiber 320 has a light quantity near the central optical axis of the optical fiber. It is desirable that the light beam is not a donut-shaped light beam that is lower than the light amount in the peripheral portion, but is a solid light beam in the vicinity of the central optical axis of the optical fiber having a light amount equivalent to that in the peripheral portion.

  The collimating optical system 330 is provided on the downstream side of the emission end of the optical fiber 320, and converts the laser light emitted from the optical fiber 320 into a parallel light beam. By converting the laser light into a parallel light beam by the collimating optical system 330, the diffusion state of the laser light can be easily controlled by the diffusion angle of the diffusion member 340 in the diffusion member 340 provided in the subsequent stage. . The configuration of the collimating optical system 330 is not particularly limited, and a known optical system for converting laser light into a parallel light beam may be configured by appropriately combining known optical elements.

  The diffusing member 340 is provided in the vicinity of the rear focal position of the collimating optical system 330, and generates a secondary light source by diffusing the parallel light beam emitted from the collimating optical system 330. That is, the light emission end of the diffusing member 340 functions as a secondary light source.

  The size of the secondary light source generated by the diffusing member 340 can be controlled by the focal length of the collimating optical system 330. Further, the NA of the emitted light can be controlled by the diffusion angle of the diffusion plate. Due to both effects, it is possible to increase the invariant of the Lagrange expressed by Equation 2 above, and to achieve both a desired light source size and a desired illumination range.

  If the size of the secondary light source is to be adjusted, the size of the secondary light source may be optimized based on the NA emitted from the optical fiber and the focal length of the collimating optical system.

  The light emitted from the diffusing member 340 is guided to the condenser optical system 350. The condenser optical system 350 forms an image of the secondary light source formed on the diffusing member 340 onto the illumination target at a predetermined paraxial lateral magnification. Examples of the illumination target include an incident end of a light guide provided in the endoscope unit, which is located on the downstream side of the condenser optical system 350. Here, unlike the conventional case, the condenser optical system 350 according to the present embodiment connects the secondary light source so as to fill the area of the illumination target (for example, the entrance end of the ride guide provided in the endoscope unit) as much as possible. Let me image. Thereby, speckle noise can be reduced as the illumination device 3 as a whole.

  The imaging magnification (paraxial lateral magnification) β of the condenser optical system 350 is expressed by the above formula 102 by the focal length f of the condenser optical system and the distance X from the focal position F to the object plane.

In addition, in the illumination device 3 according to the present embodiment, the diameter of the incident end of the light guide on which the secondary light source transmitted through the condenser optical system 350 is incident is φ _LG, and the size of the image of the secondary light source is Y ′. Then, it is preferable that the size of the image of the secondary light source is controlled so that the relationship represented by the above formula 106 is established.

  Further, the paraxial lateral magnification β of the condenser optical system 350 may be appropriately determined so that the image size Y ′ of the secondary light source satisfies the range of the above formula 106, but 0.4 ≦ β ≦ 2. 3 is more preferable.

  The configuration of the lighting device 1 according to this embodiment has been described in detail above with reference to FIG.

<About the configuration of the endoscope>
Next, a configuration of the endoscope 10 in which the illumination device 3 according to the present embodiment is used as an illumination light source will be briefly described with reference to FIG. FIG. 26 is an explanatory diagram schematically illustrating the configuration of an endoscope including the illumination device according to the present embodiment.

  The illumination device 3 as described above is used as a light source, and an image of the light source by the condenser optical system is formed on a light guide 901 provided in an arbitrary endoscope unit 900, thereby reducing illumination light with reduced speckle noise. Can be obtained. The illumination light guided to the light guide 901 is guided to the endoscope body 903 by the light guide 901 and guided to the distal end portion of the endoscope.

Here, the endoscope unit 900 to which the illumination device 3 is mounted is not particularly limited, and any endoscope unit 900 including a general light guide 901 can be used. is there. Conversely, if you want to use the endoscope unit 900 having a certain light guide 901, in response to the allowable incident numerical aperture NA _L of the light guide 901, the secondary light source image of the illumination device 1 according to this embodiment Y ′ and the paraxial lateral magnification β of the condenser optical system 350 may be set.

  The endoscope 10 including the illumination device 3 according to the present embodiment has been briefly described above with reference to FIG.

  The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the technical scope of the present disclosure is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field of the present disclosure can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that it belongs to the technical scope of the present disclosure.

  For example, in addition to those described in the third embodiment, various technical ideas described in the first embodiment can be applied to the second embodiment. Various technical ideas described in the embodiments can be applied to the first embodiment.

  Further, the effects described in the present specification are merely illustrative or exemplary and are not limited. That is, the technology according to the present disclosure can exhibit other effects that are apparent to those skilled in the art from the description of the present specification in addition to or instead of the above effects.

The following configurations also belong to the technical scope of the present disclosure.
(1)
At least one laser light source for emitting laser light;
An optical fiber on which the laser light emitted from the laser light source is incident;
A diffusion member that generates a secondary light source by diffusing the laser light emitted from the optical fiber;
With
The said laser beam is an illuminating device which injects into the incident-end surface of the said optical fiber from the diagonal direction with respect to the normal line of the said incident-end surface.
(2)
The laser beam is
Incident on the optical fiber via a coupling optical system having at least a condenser lens;
The illuminating device according to (1), wherein the light is incident on the condensing lens at a position parallel to an optical axis composed of the condensing lens and the optical fiber and off the center of the optical axis.
(3)
The laser beam is
The laser beam is incident on the optical fiber via a coupling optical system having at least a collimating lens that converts the laser light into a parallel light beam and a condenser lens that is provided at a subsequent stage of the collimating lens,
The illuminating device according to (1), wherein the light is incident on the condensing lens at a position parallel to an optical axis composed of the condensing lens and the optical fiber and off the center of the optical axis.
(4)
A plurality of the laser light sources are provided;
The laser beam having a narrow beam width of at least the parallel light flux is incident on a position parallel to the optical axis composed of the condenser lens and the optical fiber and at a position off the center of the optical axis. The lighting device described in 1.
(5)
The illumination according to any one of (1) to (4), wherein a collimator lens that makes the laser light emitted from the optical fiber a parallel light beam is disposed between the optical fiber and the diffusing member. apparatus.
(6)
The incident allowable angle of the optical fiber is θ _fiber , the condensing angle of the laser light at the incident end face of the optical fiber is θ _beam, and the optical axis of the optical fiber at the incident end face of the optical fiber and the center of the laser light The illumination device according to any one of (1) to (5), wherein the relationship represented by the following Expression 1 is established when the angle formed with the optical axis is θ.

(Θ + θ _beam ) ≦ θ _fiber (Formula 1)

(7)
When the converging angle of the laser light at the incident end face of the optical fiber is θ _beam, and the angle between the optical axis of the optical fiber and the central optical axis of the laser light at the incident end face of the optical fiber is θ The lighting device according to any one of (1) to (6), wherein a relationship represented by the following expression 1-2 is established.

θ ≦ θ _beam (Formula 1-2)

(8)
When the beam width of the parallel light beam is W _A , the focal length of the condenser lens is f, the allowable incidence angle of the optical fiber is θ _fiber, and the shift amount from the center of the optical axis is D _A The lighting device according to any one of (3) to (5), wherein a relationship represented by the following expression 2 is established.

(W _A / 2) + D _A ≦ (f × sin (θ _fiber )) (Equation 2)

(9)
When the beam width of the parallel light beam is W _A and the shift amount from the center of the optical axis is D _A , the relationship represented by the following expression 2-2 is established, (3) to (5), The lighting device according to any one of (8).

D _A ≦ (W _A / 2) (Formula 2-2)

(10)
In the cross section orthogonal to the optical axis, each of the parallel light fluxes is inscribed in one circle centered on the optical axis, according to any one of (4), (5), and (8). Lighting device.
(11)
The lighting device according to any one of (4), (5), and (9), wherein each of the parallel light beams includes the optical axis in a cross section orthogonal to the optical axis.
(12)
The wavelength of the said laser beam inject | emitted from these laser light sources is an illuminating device as described in any one of (4), (5), (10), (11) which comprises at least white light.
(13)
The illumination device according to any one of (1) to (12), wherein the diffusion member is a diffusion plate or a bundle fiber.
(14)
The said laser light source is an illuminating device as described in any one of (1)-(13) which is a semiconductor laser or a solid-state laser.
(15)
Guiding laser light emitted from at least one laser light source to an optical fiber;
Diffusing the laser light emitted from the optical fiber with a diffusing element to generate a secondary light source;
Including
The illumination method, wherein the laser light is incident on an incident end face of the optical fiber from an oblique direction with respect to a normal line of the incident end face.
(16)
At least one laser light source for emitting laser light;
An optical fiber on which the laser light emitted from the laser light source is incident;
A diffusing element that generates a secondary light source by diffusing the laser light emitted from the optical fiber;
With
The endoscope comprising an illuminating device that is incident on an incident end face of the optical fiber from an oblique direction with respect to a normal line of the incident end face.

1, 2, 3 Illumination device 100, 200, 300 Laser light source 110, 210, 310 Coupling optical system 120, 220, 320 Optical fiber 130, 230, 330 Collimating optical system 140, 240, 340 Diffusing member 150, 250, 350 Condenser Optical system

Claims (16)

At least one laser light source for emitting laser light;
An optical fiber on which the laser light emitted from the laser light source is incident;
A diffusion member that generates a secondary light source by diffusing the laser light emitted from the optical fiber;
With
The said laser beam is an illuminating device which injects into the incident-end surface of the said optical fiber from the diagonal direction with respect to the normal line of the said incident-end surface. The laser beam is
Incident on the optical fiber via a coupling optical system having at least a condenser lens;
2. The illumination device according to claim 1, wherein the illumination device is incident on the condensing lens at a position parallel to an optical axis composed of the condensing lens and the optical fiber and off a center of the optical axis. The laser beam is
The laser beam is incident on the optical fiber via a coupling optical system having at least a collimating lens that converts the laser light into a parallel light beam and a condenser lens that is provided at a subsequent stage of the collimating lens,
2. The illumination device according to claim 1, wherein the illumination device is incident on the condensing lens at a position parallel to an optical axis composed of the condensing lens and the optical fiber and off a center of the optical axis. A plurality of the laser light sources are provided;
The laser beam having a narrow beam width of at least the parallel light beam is incident on a position parallel to the optical axis composed of the condenser lens and the optical fiber and at a position off the center of the optical axis. The lighting device described in 1.   The illuminating device according to claim 1, wherein a collimator lens that makes the laser beam emitted from the optical fiber a parallel light beam is disposed between the optical fiber and the diffusing member. The incident allowable angle of the optical fiber is θ _fiber , the condensing angle of the laser light at the incident end face of the optical fiber is θ _beam, and the optical axis of the optical fiber at the incident end face of the optical fiber and the center of the laser light The lighting device according to claim 1, wherein a relationship represented by the following expression 1 is established when an angle formed with the optical axis is θ.

(Θ + θ _beam ) ≦ θ _fiber (Formula 1) When the converging angle of the laser light at the incident end face of the optical fiber is θ _beam, and the angle between the optical axis of the optical fiber and the central optical axis of the laser light at the incident end face of the optical fiber is θ The lighting device according to claim 1, wherein a relationship represented by the following expression 1-2 is established.

θ ≦ θ _beam (Formula 1-2)
When the beam width of the parallel light beam is W _A , the focal length of the condenser lens is f, the allowable incidence angle of the optical fiber is θ _fiber, and the shift amount from the center of the optical axis is D _A The lighting device according to claim 3, wherein a relationship represented by the following expression 2 is established.

(W _A / 2) + D _A ≦ (f × sin (θ _fiber )) (Equation 2) 4. The illumination device according to claim 3, wherein when the beam width of the parallel light flux is W _A and the shift amount from the center of the optical axis is D _A , the relationship represented by the following Expression 2-2 is satisfied. .

D _A ≦ (W _A / 2) (Formula 2-2)
  5. The illumination device according to claim 4, wherein each of the parallel light beams is inscribed in one circle centered on the optical axis in a cross section orthogonal to the optical axis.   The lighting device according to claim 4, wherein each of the parallel light beams includes the optical axis in a cross section orthogonal to the optical axis.   The illumination device according to claim 4, wherein a wavelength of the laser light emitted from the plurality of laser light sources constitutes at least white light.   The lighting device according to claim 1, wherein the diffusion member is a diffusion plate or a bundle fiber.   The illumination device according to claim 1, wherein the laser light source is a semiconductor laser or a solid-state laser. Guiding laser light emitted from at least one laser light source to an optical fiber;
Diffusing the laser light emitted from the optical fiber with a diffusing element to generate a secondary light source;
Including
The illumination method, wherein the laser light is incident on an incident end face of the optical fiber from an oblique direction with respect to a normal line of the incident end face. At least one laser light source for emitting laser light;
An optical fiber on which the laser light emitted from the laser light source is incident;
A diffusing element that generates a secondary light source by diffusing the laser light emitted from the optical fiber;
With
The endoscope comprising an illuminating device that is incident on an incident end face of the optical fiber from an oblique direction with respect to a normal line of the incident end face.

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